1. Field of the Invention
The present invention relates to a capacitive input device used as, for example, a pointing device for a personal computer.
2. Description of the Related Art
FIG. 11 is a schematic cross-sectional view of an input device 100 in the related art. The input device 100 is a pad-type pointing device for use in notebook-type personal computers.
In the input device 100 shown in FIG. 11, an X electrode layer 103 having a plurality of X electrodes 102 is formed on the upper surface of a synthetic resin film board (sensor board) 101, and a Y electrode layer 105 having a plurality of Y electrodes 104 is formed on the lower surface of the film board 101, such that the X electrodes 102 and the Y electrodes 104 are arranged into a matrix. The X electrode layer 103 and the Y electrode layer 105 are covered with insulating films 106 and 107, respectively. A top sheet 108 is provided above the X electrode layer 103 serving as a sensing surface. The electrode layers 103 and 105, the insulating films 106 and 107, and the top sheet 108 are rectangular with the same dimension.
The input device 100 further includes a control circuit board 110 on the bottom layer opposite to the top sheet 108. The control circuit board 110 is also rectangular with the same dimension as the film board 101. A control circuit 111 is formed on a surface of the control circuit board 110 that is farthest from the film board 101.
In the input device 100, through-holes (not shown) are formed in the film board 101, the insulating film 107, and the control circuit board 110. This allows the X electrode layer 103 and the Y electrode layer 105 to be electrically connected with each other so that a signal in response to capacitance detected between the X electrode layer 103 and the Y electrode layer 105 is passed to the control circuit 111.
However, the electrode layers 103 and 105, and the film board 101 overlie the control circuit board 110, thus making the related art input device 100 thick. A notebook-type personal computer (PC) incorporating such a thick input device 100 cannot be thin. Moreover, the control circuit board 110 has the same size and area as the film board 101, leading to increased cost.